[revol]

On the bench I've got a B6 and a B6D. The box in the B6D is very free and smooth, the B6 is a little tight and not quite as smooth as the B6D.
Is this normal or should both be the same and the B6 has a problem?
I'd have though that they should both spin freely and smoothly as they're both 3 gear systems rather than belts.

Thanks.